Temporarily disable all foreign key constraints - sql-server

Question

I am running an SSIS package which will replace data for a few tables from FlatFiles to existing tables in a database.
My package will truncate the tables and then insert the new data. When I run my SSIS package, I get an exception because of the foreign keys.
Can I disable the constraints, run my import, then re-enable them?

Answer 1

To disable foreign key constraints:
DECLARE #sql nvarchar(max) = N'';
;WITH x AS
(
SELECT DISTINCT obj =
QUOTENAME(OBJECT_SCHEMA_NAME(parent_object_id)) + '.'
+ QUOTENAME(OBJECT_NAME(parent_object_id))
FROM sys.foreign_keys
)
SELECT #sql += N'ALTER TABLE ' + obj + N' NOCHECK CONSTRAINT ALL;
' FROM x;
EXEC sys.sp_executesql #sql;
To re-enable:
DECLARE #sql nvarchar(max) = N'';
;WITH x AS
(
SELECT DISTINCT obj =
QUOTENAME(OBJECT_SCHEMA_NAME(parent_object_id)) + '.'
+ QUOTENAME(OBJECT_NAME(parent_object_id))
FROM sys.foreign_keys
)
SELECT #sql += N'ALTER TABLE ' + obj + N' WITH CHECK CHECK CONSTRAINT ALL;
' FROM x;
EXEC sys.sp_executesql #sql;
However, you will not be able to truncate the tables, you will have to delete from them in the right order. If you need to truncate them, you need to drop the constraints entirely, and re-create them. This is simple to do if your foreign key constraints are all simple, single-column constraints, but definitely more complex if there are multiple columns involved.
Here is something you can try. In order to make this a part of your SSIS package you'll need a place to store the FK definitions while the SSIS package runs (you won't be able to do this all in one script). So in some utility database, create a table:
CREATE TABLE dbo.PostCommand(cmd nvarchar(max));
Then in your database, you can have a stored procedure that does this:
DELETE other_database.dbo.PostCommand;
DECLARE #sql nvarchar(max) = N'';
SELECT #sql += N'ALTER TABLE '
+ QUOTENAME(OBJECT_SCHEMA_NAME(fk.parent_object_id))
+ '.' + QUOTENAME(OBJECT_NAME(fk.parent_object_id))
+ ' ADD CONSTRAINT ' + fk.name + ' FOREIGN KEY ('
+ STUFF((SELECT ',' + c.name
FROM sys.columns AS c
INNER JOIN sys.foreign_key_columns AS fkc
ON fkc.parent_column_id = c.column_id
AND fkc.parent_object_id = c.[object_id]
WHERE fkc.constraint_object_id = fk.[object_id]
ORDER BY fkc.constraint_column_id
FOR XML PATH(''),
TYPE).value(N'./text()[1]', 'nvarchar(max)'), 1, 1, N'')
+ ') REFERENCES ' +
QUOTENAME(OBJECT_SCHEMA_NAME(fk.referenced_object_id))
+ '.' + QUOTENAME(OBJECT_NAME(fk.referenced_object_id))
+ '(' +
STUFF((SELECT ',' + c.name
FROM sys.columns AS c
INNER JOIN sys.foreign_key_columns AS fkc
ON fkc.referenced_column_id = c.column_id
AND fkc.referenced_object_id = c.[object_id]
WHERE fkc.constraint_object_id = fk.[object_id]
ORDER BY fkc.constraint_column_id
FOR XML PATH(''),
TYPE).value(N'./text()[1]', N'nvarchar(max)'), 1, 1, N'') + ');
' FROM sys.foreign_keys AS fk
WHERE OBJECTPROPERTY(parent_object_id, 'IsMsShipped') = 0;
INSERT other_database.dbo.PostCommand(cmd) SELECT #sql;
IF ##ROWCOUNT = 1
BEGIN
SET #sql = N'';
SELECT #sql += N'ALTER TABLE ' + QUOTENAME(OBJECT_SCHEMA_NAME(fk.parent_object_id))
+ '.' + QUOTENAME(OBJECT_NAME(fk.parent_object_id))
+ ' DROP CONSTRAINT ' + fk.name + ';
' FROM sys.foreign_keys AS fk;
EXEC sys.sp_executesql #sql;
END
Now when your SSIS package is finished, it should call a different stored procedure, which does:
DECLARE #sql nvarchar(max);
SELECT #sql = cmd FROM other_database.dbo.PostCommand;
EXEC sys.sp_executesql #sql;
If you're doing all of this just for the sake of being able to truncate instead of delete, I suggest just taking the hit and running a delete. Maybe use bulk-logged recovery model to minimize the impact of the log. In general I don't see how this solution will be all that much faster than just using a delete in the right order.
In 2014 I published a more elaborate post about this here:
Drop and Re-Create All Foreign Key Constraints in SQL Server

Answer 2

Use the built-in sp_msforeachtable stored procedure.
To disable all constraints:
EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT ALL";
To enable all constraints:
EXEC sp_msforeachtable "ALTER TABLE ? WITH CHECK CHECK CONSTRAINT ALL";
To drop all the tables:
EXEC sp_msforeachtable "DROP TABLE ?";

Answer 3

A good reference is given at : http://msdn.microsoft.com/en-us/magazine/cc163442.aspx
under the section "Disabling All Foreign Keys"
Inspired from it, an approach can be made by creating a temporary table and inserting the constraints in that table, and then dropping the constraints and then reapplying them from that temporary table. Enough said here is what i am talking about
SET NOCOUNT ON
DECLARE #temptable TABLE(
Id INT PRIMARY KEY IDENTITY(1, 1),
FKConstraintName VARCHAR(255),
FKConstraintTableSchema VARCHAR(255),
FKConstraintTableName VARCHAR(255),
FKConstraintColumnName VARCHAR(255),
PKConstraintName VARCHAR(255),
PKConstraintTableSchema VARCHAR(255),
PKConstraintTableName VARCHAR(255),
PKConstraintColumnName VARCHAR(255)
)
INSERT INTO #temptable(FKConstraintName, FKConstraintTableSchema, FKConstraintTableName, FKConstraintColumnName)
SELECT
KeyColumnUsage.CONSTRAINT_NAME,
KeyColumnUsage.TABLE_SCHEMA,
KeyColumnUsage.TABLE_NAME,
KeyColumnUsage.COLUMN_NAME
FROM
INFORMATION_SCHEMA.KEY_COLUMN_USAGE KeyColumnUsage
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TableConstraints
ON KeyColumnUsage.CONSTRAINT_NAME = TableConstraints.CONSTRAINT_NAME
WHERE
TableConstraints.CONSTRAINT_TYPE = 'FOREIGN KEY'
UPDATE #temptable SET
PKConstraintName = UNIQUE_CONSTRAINT_NAME
FROM
#temptable tt
INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS ReferentialConstraint
ON tt.FKConstraintName = ReferentialConstraint.CONSTRAINT_NAME
UPDATE #temptable SET
PKConstraintTableSchema = TABLE_SCHEMA,
PKConstraintTableName = TABLE_NAME
FROM #temptable tt
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TableConstraints
ON tt.PKConstraintName = TableConstraints.CONSTRAINT_NAME
UPDATE #temptable SET
PKConstraintColumnName = COLUMN_NAME
FROM #temptable tt
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KeyColumnUsage
ON tt.PKConstraintName = KeyColumnUsage.CONSTRAINT_NAME
--Now to drop constraint:
SELECT
'
ALTER TABLE [' + FKConstraintTableSchema + '].[' + FKConstraintTableName + ']
DROP CONSTRAINT ' + FKConstraintName + '
GO'
FROM
#temptable
--Finally to add constraint:
SELECT
'
ALTER TABLE [' + FKConstraintTableSchema + '].[' + FKConstraintTableName + ']
ADD CONSTRAINT ' + FKConstraintName + ' FOREIGN KEY(' + FKConstraintColumnName + ') REFERENCES [' + PKConstraintTableSchema + '].[' + PKConstraintTableName + '](' + PKConstraintColumnName + ')
GO'
FROM
#temptable
GO

Answer 4

There is an easy way to this.
-- Disable all the constraint in database
EXEC sp_msforeachtable 'ALTER TABLE ? NOCHECK CONSTRAINT all'
-- Enable all the constraint in database
EXEC sp_msforeachtable 'ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all'
Reference SQL SERVER – Disable All the Foreign Key Constraint in Database – Enable All the Foreign Key Constraint in Database

Answer 5

Disable all table constraints
ALTER TABLE TableName NOCHECK CONSTRAINT ConstraintName
-- Enable all table constraints
ALTER TABLE TableName CHECK CONSTRAINT ConstraintName

Answer 6

In case you use a different database schemas than ".dbo" or your db is containing Pk´s, which are composed by several fields, please don´t use the the solution of Carter Medlin, otherwise you will damage your db!!!
When you are working with different schemas try this (don´t forget to make a backup of your database before!):
DECLARE #sql AS NVARCHAR(max)=''
select #sql = #sql +
'ALTER INDEX ALL ON ' + SCHEMA_NAME( t.schema_id) +'.'+ '['+ t.[name] + '] DISABLE;'+CHAR(13)
from
sys.tables t
where type='u'
select #sql = #sql +
'ALTER INDEX ' + i.[name] + ' ON ' + SCHEMA_NAME( t.schema_id) +'.'+'[' + t.[name] + '] REBUILD;'+CHAR(13)
from
sys.key_constraints i
join
sys.tables t on i.parent_object_id=t.object_id
where i.type='PK'
exec dbo.sp_executesql #sql;
go
After doing some Fk-free actions, you can switch back with
DECLARE #sql AS NVARCHAR(max)=''
select #sql = #sql +
'ALTER INDEX ALL ON ' + SCHEMA_NAME( t.schema_id) +'.'+'[' + t.[name] + '] REBUILD;'+CHAR(13)
from
sys.tables t
where type='u'
print #sql
exec dbo.sp_executesql #sql;
exec sp_msforeachtable "ALTER TABLE ? WITH NOCHECK CHECK CONSTRAINT ALL";

Answer 7

not need to run queries to sidable FKs on sql. If you have a FK from table A to B, you should:
delete data from table A
delete data from table B
insert data on B
insert data on A
You can also tell the destination not to check constraints

Answer 8

Truncating the table wont be possible even if you disable the foreign keys.so you can use
delete command to remove all the records from the table,but be aware if you are using delete
command for a table which consists of millions of records then your package will be slow
and your transaction log size will increase and it may fill up your valuable disk space.
If you drop the constraints it may happen that you will fill up your table with unclean data
and when you try to recreate the constraints it may not allow you to as it will give errors.
so make sure that if you drop the constraints,you are loading data which are correctly related to each other and satisfy the constraint relations which you are going to recreate.
so please carefully think the pros and cons of each method and use it according to your requirements

Answer 9

Disable all indexes (including the pk, which will disable all fks), then reenable the pks.
DECLARE #sql AS NVARCHAR(max)=''
select #sql = #sql +
'ALTER INDEX ALL ON [' + t.[name] + '] DISABLE;'+CHAR(13)
from
sys.tables t
where type='u'
select #sql = #sql +
'ALTER INDEX ' + i.[name] + ' ON [' + t.[name] + '] REBUILD;'+CHAR(13)
from
sys.key_constraints i
join
sys.tables t on i.parent_object_id=t.object_id
where
i.type='PK'
exec dbo.sp_executesql #sql;
go
[Do your data load]
Then bring everything back to life...
DECLARE #sql AS NVARCHAR(max)=''
select #sql = #sql +
'ALTER INDEX ALL ON [' + t.[name] + '] REBUILD;'+CHAR(13)
from
sys.tables t
where type='u'
exec dbo.sp_executesql #sql;
go